Organic light emitting diodes and devices (OLEDs) have begun to attract great interest for a number of applications. For example, attempts have been made to incorporate organic light emitting diodes in display devices. Organic light emitting diode devices can potentially offer a number of advantages over other types of display technologies. In particular, compared with certain types of display technologies, organic light emitting diode devices have the potential to offer lower manufacturing costs, reduced energy requirements, and improved visual characteristics.
However, existing organic light emitting devices often suffer from a number of problems. Existing organic light emitting diode devices are typically formed by depositing multiple organic layers on a substrate. The requirement of multiple organic layers can result in added weight and additional manufacturing costs. Also, the organic layers are sometimes formed from amorphous or randomly oriented polymeric materials. As a result of such random orientation, electrical conductivity of the organic layers can be inadequate, and charged species can travel in three dimensions relatively great distances along the randomly oriented polymeric materials before reaching a fluorescent or phosphorescent species that can emit light. At the same time, such random orientation can lead to the formation of “micro-wells” that can act as capacitors to further lower the electrical conductivity of the organic layers. To produce light having a desired brightness, a greater electric field density is sometimes applied to the organic layers, which electric field density can lead to thermal breakdown or instability of the organic layers. In addition, as the material draws in more current to achieve emission, UV light is emitted by the OLED material that can react with oxygen from absorbed moisture, causing radicals to form, which radicals react with the OLED material, effectively cross-linking the material, and may remove the OLED material from the surface.
U.S. Patents which illustrate various approaches to OLEDs and image display devices include e.g., U.S. Pat. No. 6,656,608 to Kita et al.; U.S. Pat. No. 6,361,885 to Chou; U.S. Pat. No. 5,677,545 to Shi et al.; U.S. Pat. No. 5,811,833 to Thompson; U.S. Pat. No. 5,946,550 to Papadimitrakopoulos; U.S. Pat. No. 6,045,930 to Thompson et al.; U.S. Pat. No. 6,251,303 to Bawendi et al.; U.S. Pat. No. 6,391,426 to Bawendi et al; U.S. Pat. No. 6,406,804 to Higashi et al.; U.S. Pat. No. 4,451,455 to Thompson et al.; U.S. Pat. No. 6,458,475 to Adachi et al.; U.S. patent application Ser. No. 2001/0005021A1 to Fukuyama et al.; U.S. patent application Ser. No. 2002/0042174 to Kunugi et al.; U.S. Pat. No. 6,030,700 to S. R. Forrest et al.; U.S. Pat. No. 6,232,714 to Shen et al.; U.S. Pat. No. 5,294,870 to C. W. Tang et al.; U.S. Pat. No. 6,245,393 to M. E. Thompson et al.; and U.S. Pat. No. 6,048,630 to Burrows et al.
References which describe various approaches to conductive organic molecules are: U.S. patent application Ser. No. 2002/0064683 to Okada et al.; U.S. Pat. No. 4,197,142 to Bolton et al.; U.S. Pat. No. 6,492,096 to Liu et al.; U.S. Pat. No. 6,479,240 to Kayyem et al.; U.S. Pat. No. 6,430,511 to Tour et al.; U.S. Pat. No. 6,348,700 to Ellenbogen et al.; U.S. Pat. No. 6,339,227 to Ellenbogen et al.; U.S. Pat. No. 6,169,291 to Metzger et al.; U.S. Pat. No. 6,096,273 to Kayyem et al.; U.S. Pat. No. 6,060,327 to Keen et al.; U.S. Pat. No. 6,028,265 to Ono et al.; U.S. Pat. No. 5,525,811 to Sakurai et al.; U.S. Pat. No. 5,057,878 to Geddes et al.; U.S. Pat. No. 5,010,451 to Ueyama et al; Liu, et al. Synthetic Metals, 122 (2001) 177-179; Ramachandran, et al., Science, 300 (2003) 1413-1416; Blum, et al. AppI. Phys. Lett. 82 (2003) 3322-3324; Nitzan, et al., Science 300 (2003), 1384-1389.
It is against this background that a need arose to develop the light emitting molecules and organic light emitting devices described herein.